Kin 236 Exam #2 Learning Objectives and Study Guide

Impulse - momentum relationship

impulse is equal to the change in the momentum of the object that the impulse acts on.

Static vs Dynamic balance

-static- equilibrium while stationary -dynamic- maintaining equilibrium while in motion, from one foot to the other and everything in control or from CoM to one foot

Role of vision

3 Phases 1. movement preparation --> movement important for planning 2. Movement initiation --> initial flight ballistic, open loop, vision less important 3. movement termination --> feedback as target is approached, closed loop, vision is important

Law of Acceleration

A force applied to a body causes it to accelerate with a magnitude proportional to the force and inversely proportional to its mass

The movement of the center of mass in running can be modeled as?

A mass spring system

A motor unit consists of

A single motor unit and the muscle fibers that innervate it

Measurement Error • Accuracy vs Precision

Accuracy --> how close you are to the target Precision --> how the data points are to the other data points

Law of gravity

All bodies are attracted to each other with a force proportional to the product of the masses and inversely proportional to the square of the distance between them

Which analysis tool is used to asses coordination?

Angle - Angle diagram, cross correlation, relative phase angle

fMRI

Based upon different magnetic properties of hemoglobin with and without oxygen + Good spatial resolution + Full brain - Indirect measure, poor temporal resolution - Movements limited to supine within scanner

Systems of Postural Control ▪ Biomechanical constraints ▪ Limits of stability ▪ Postural Responses ▪ Hip vs Ankle vs Stepping ▪ Sensory Integration ▪ Relative contributions for firm vs unstable surface

Biomechanical constraints --> keep CoM within base of support, stability margin in stropped posture (less range of motion) vs normal posture (more free range of motion) Limits of stability --> How far people can move forwards or backwards, healthy people are more likely to get a full range of motion, multisensory loss people are less likely to reach a max in range of motion Postural Responses Hip --> Body torques at hips, Unstable surface, Perturbations, fast & large Ankle --> Body = inverted pendulum, Firm Surface, Perturbations, slow & small Stepping --> Step to recover equilibrium, Used to prevent a fall, Preferred when ankle strategy fails to correct movement Sensory Integration Firm Surface --> 70% somatosensory 20% vestibular 10% vision Unstable Surface --> 60% vestibular 30% vision 10% somatosensory

Center of mass (COM), Center of gravity (COG)

CoM --> It is the average position of all the parts of the system, CoG --> hypothetical point around which the force of gravity appears to act. It is point at which the combined mass of the body appears to be concentrated.

Control of Gait Dynamics

During turning and non-straight movements, the COM often falls outside the BOS Movements must be adjusted for inertial forces

Wa;king is different than running in that

During walking there is a double support has but there is no flight phase

Which of the following techniques can be used to study the timing of cortical activity in response to an event (e.g. a buzzer)?

EEG (electric activity --> direct measurement of activity)

The concept of motor equivalence explains why your signature is never exactly the same

False

Running --> Spring Mass Model (Potential energy + Kinetic energy - exchange)

Fluctuations in the same pattern/phase, mid stance has low PE and KE in Achilles tendon allowing force to fire back, swing phase --> leg spring that stretches tendon to load and during unloading produces the force, Mechanical energy --> elastic energy stored and released in the tendons

Law of Reaction

For every action there is an equal and opposite reaction

The impulse - momentum relationship describes the effects of a

Force applied over a period of time

Force, momentum, impulse

Force: any interaction that tends to maintain or alter the motion of a rigid body or to distort a non-rigid body, any interaction that tends to maintain or alter the motion of a rigid body Momentum: measure of the state of motion, product of mass and velocity, L = mv Impulse: Force applied for a time, product of force and time, Impulse = Ft

CNS --> function, brain (important structures), spinal cord

Function --> control center that recieves and integrates info from the body and sends signals to all parts of the body (through he brain and spinal cord) Brian --> cerebral cortex is involved in planning and execution of voluntary movement, Cerebellum --> plays important role in integration and fine tuning of movement (coordination and timing), motor and somatosensory regions --> different parts innervate different parts of body, determines effects of injuries to brain Spinal cord --> relays messages between brain and periphery

Ground Reaction Force (GRF), Center of Pressure (COP)

GRF --> equal in magnitude and opposite in direction to the force that the body exerts on the supporting surface through the foot CoP --> the average point that a force gets applied to, balance relies on it, ex: your foot when walking

Speed - accuracy tradeoff Fitts Law • Index of difficulty

Increase speed --> less accurate, Slow speed --> increase accuracy

Performance production measures • Kinematics • Kinetics • EMG

Kinematics --> outcome measures to explain outcomes Kinetics --> Forces to explain outcomes EMG --> Where muscle activity is measured in pros vs regular people

Motion: linear and angular

Linear: applies to points, translation Angular: rotation, The motion of a body about a fixed point or fixed axis, It is equal to the angle passed over at the point or axis by a line drawn to the body.

Mass, Center of Mass, Inertia, Moment of Inertia

Mass: Center of Mass: Moment Inertia:

The product of force and displacement in the direction of the applied force is called

Mechanical Work

Vestibular system (Understand sensitivity to angle, acceleration and rotational acceleration)

Morphological polarization of hair cells in the utricular and saccular maculae, Recptors in the ampulla are stimulated by angular accelerations and the fluid moves after motion stops due to interia, sensitive to acceleration and position and head tilts

Motor Control vs Motor Coordination • Angle - Angle diagrams • Cross correlation • Relative phase (no details)

Motor control --> how and individual controls an individual unit-muscle segment, joint Motor coordination --> multiple units, how they are controlled together to produce purposeful movement Angle - Angle diagrams --> a qualitative plot showing the dynamics of a movement pattern over multiple trials. Cross correlation --> a measurement that tracks the movements of two or more sets of time series data relative to one another Relative Phase --> e measures the relationship between two joint or body segment angles to characterize inter-joint coordination patterns.

Manual aiming skills

Motor skills that involve arm, hand, and finger movement to target, ex: typing on a keyboard, using a key in a door neeeds limb movement accuracy, sometimes need speed, * any arm movement with a specific end task (ex: picking up a water bottle)

The gradation of muscle force is controlled by the nervous system using the mechanisms of

Motor unit recruitment and rate coding

In a reaction time test, the time from initiation of the response to the termination of the response is called:

Movement time

Walking --> inverted pendulum model (potential energy vs. kinetic energy - exchange)

No additional work is needed, pendulums don't need muscles --> only need to redirect energy to walk, kinetic energy is lowest in the stance phase, out of phase --> PE and KE out of phase, PE highest/KE lowest in single support

EEG

Non-invasive technique that records electrical activity from electrodes placed on scalp • Described changes in frequency-specific electrical activity during awake periods and sleep + Direct measure, good temporal resolution (when) + Mobile (but movement artefacts) - Poor spatial resolution (where) - Limited to areas close to scalp

PET

Non-invasive, nuclear imaging technique that produces images reflecting metabolic processes (of the brain/body) • Measures the relative concentration of introduced radioactively labeled probes + Good spatial resolution + Full brain - Indirect measure (based on blood flow), poor temporal resolution - Movements limited to supine within scanner (or not, but then no temporal information at all) - Radioactivity

Movement control "classes"

Open loop control --> all movement control contained in initial CNS instructions --> ballistic, too fast/short/out of sight so with movement on initial command, once you start moving/innate so you can't adjust Closed loop --> movement control is updated based on feedback and comparison to a plan, continuous, feedback - visual, proprioception depends on time available

Cost of transport --> preferred walking speed and walk-run transition

Preferred walking speed is 1.2 m/s bc it is the most efficient speed to minimize energy cost, It takes more energy to walk 1 m/s than it does to stand still and less if you go fast because you cover a greater distance at a quicker rate At most speeds you can comfortably walk bc running is more costly. As a certain speed (roughly 2 m/s) running is more energy efficient (has a lower energy cost when compared to walking) and this is the walk-un transition --> running becomes less metabolically expensive than walking.

• What is the purpose of a Stroop task in research settings • Give 2 examples of stroop tasks in different domains • Describe the concept of a Stroop task

Purpose is to see if something makes people thing about effects their motor ability, 2 examples: audutory and visual domains (color, numbers, etc.), concept: think about colors of different fonts of words and have to pay attention to which is correct

Postural Control Quasi-static

Push on the ground with tows to keep yourself from falling forward, CoP corrects CoM motion and keeps CoM away from edges of BoS, When solid line goes above the dotted line the body goes forward and vice versa when it goes backward, near static conditions, slow enough to be considered individual static positions, maintain desired body position

Functions of the nervous system

Receives sensory info about the body and enviornment, provides motor commands to the muscles, plays a major role in learning and controlling movements

What feature of walking is a main consideration in conserving ,technical and metabolic energy?

Recprical, put of phase fluctuation of kinetic and potential energy (Running would include potential/elastic energy)

Control systems: Reflexive, Postural, Intentional

Reflexive: Stumbling and stepping on something hot/sharp, Sense pain then flexor muscles activated to reflex extensor muscles and activate other leg to take over body weight, flexor reflex on one side and crossed extensor reflex on the other leg (subconscious) Postural: Brainstem: anticipatory maintenance/control of body posture when muscle is activated first, calf/gastrocnemius because the lever pulls back and the gastrocnemius kept you still and otherwise you pull yourself into a wall (subconscious), depends on info from vestibular and muscle control Intentional: Decide how to/whay to do/pick up, conscious

Response Time • Reaction Time • Premotor Time • Motor Time • Movement Time • Different types of reaction time tasks

Response time --> time between signal to start and movement completion Reaction time --> time between signal and initiation of movement (people can not respond to external signals in less than 0.100 seconds) Premotor time --> time between signal to start and EMG detection Motor time --> time between EMG detection and movement initiation Movement time --> time between movement initiation and completion

Running --> Phases of the gait cycle

Single support and flight phases, Center of Mass is lowest in single and highest in mid stance, PE and KE in phase, CoM at highest point with most speed during flight phase

Sensory system components

Some sensory systems are relevant for motor control, Exteroception (sense external environment)--> vision, hearing, cutaneous receptors, Proprioception (sense internal environment (ex: sharp turn)) --> vestibular system, golgi tendon organ, muscle spindle, joint receptors (internal touch for joint angles or forces)

Error measurement • spatial vs temporal • Consistency vs bias

Spatial --> distance of performance from goal, ex: darts - aim for 20 and hit 1 Temporal --> ex: imagine a baseball batter that swings and misses a fastball, not hitting your goal Consistency --> how far the data is spread out Bias --> where the date ends up (all at the same/simular point is a strong bias)

Walking --> Global timing of different phases of the gait cycle

Standing and swing phases of walking, 60% of the time in stance and 40% of the time in swing phase, leg flexed in swin and extended in stance, time spent in each phase in a basic description of movement sequence (stride: 0.92 sec, stance 0.55 sec, swing 0.37 sec), double stance --> 20% and duration is 0.09 sec.

TMS

TMS uses magnetic fields to induce "eddy currents" in the brain

Absolute error (AE) refers to

The absolute average distance to a target

Motor system

The motor unit: a single motor neuron and all of the muscle fibers it innervates --> represents smallest functional unit of neuromuscular system, each motor unit has between 10's - 1000's of muscle fibers --> distributing fibers to multiple mu's allows for both units to thrive longer, MU's classified by properties --> fast twitch and slow twitch

Time to contact

The use of visual information to help proper contact with the environment when in motion, ex: diving birds over the ocean, long jumper approaching take-off board makes stride adjustments based on optical information, time to contact is equivalent to amount of view object takes up divided by velocity --> far away has smaller view and closer has bigger and shorter time to get there --> ex: catching, striking, throwing, posture

Angular Impulse

Torque applied for a time, product of torque and time, Angular Impulse = Tt

PNS --> function, components, types of neurons, neuron components, reflexes and CPGS

Transmits info to and from the CNS, network of nerves that run between the spinal cord and all parts of the body, 2 components (sensory (afferent) and motor (efferent) Types of neurons --> sensory --> run from stimulus receptors to the CNS, motor --> run from CNS to muscles and glands, Interneurons --> within the cns, recieve input from sensory neurons or other interneurons, act upon motor neurons or other interneurons CPGS --> SOme spinal networks that can generate patterns of rythmic activity without external feedback or supraspinal control, sensory feedback and the brain will both exert an influence on the output from CPG

• Bimanual coordination

Use of two arms simultaneously Symmetric --> easier (because of bimanual coupling), doing the same motion with both arms Asymmetric --> harder, doing a different motion with each arm

Postural Control

Using righting and equilibrium adjustments to maintain balance during functional movements, control of a bodies position and velocity in space with respect to the base of support, duel purpose of orientation and equilibrium

Work - energy relationship

Work done on a body by a force changes its energy level

Kinetic Scalars: Energy, Work, Power

Work: units: newton meters or Joules, Change in energy, W=FD Energy: units: Joules, KineticEnergy, KE =mv2 2, PE = mgh Power: Rate of doing work = Fv, Rate of change in energy

Motor equivalence

Wrist joint is similar/same as wrist and shoulder when writing a signature --> can reproduce the same movement when writing on paper as when on a chalk board

Law of Interia

an object at rest and an object in motion will continue unless an unbalance force acts upon it.

A movement pattern that does not rely on sensory feedback would be classified as

an open loop control task

Which of the following techniques can not be used to study cortical activity during walking?

fMRI

A force vector is defined by its

magnitude, direction, point of application

Angular Momentum

measure of the rotational state of motion, product of moment of inertia and angular velocity, L = I

Factors involved with control of movement

motion capture or IMUs used for detection

According to Fitts's law, if a dart thrower took two steps backward from her regular throwing position:

movement time would increase

Base of Support (BOS)

part of the body that is in contact with the supporting surface, es: feet when standing on the ground with both feet

The nervous system

receives sensory information about the body, receives sensory information about the environment, provides motor commands to the muscles

Moment of Force (Torque)

the ability of force to produce rotation around an axis

Cognitive Control

the ability to direct thought in accord with one's intentions

Prehension

the action of reaching for and grasping an object 3 components: transport, grasp, object manipulation functional goal Transport and grasp: coupled temporarily and synergistically, EX: 1 grasp characteristics influence movement time, 2 group opening maximal at 2/3 of movement time Object manipulation: Shapes transport and grasp, EX: drinking from bottle Obeys fitts law: "accuracy involves more than target width"

fNIRS

• Functional Near-Infrared Spectroscopy (fNIR or fNIRS) • Simplest form: Exploits different rates of light absorption to distinguish concentration of oxygenated and deoxygenated hemoglobin + Fair spatial resolution + Mobile - Indirect measure, poor temporal resolution - Limited to areas close to scalp

MEG

• MEG measures magnetic fields generated by neural currents. + Direct measure, very high temporal resolution - Stationary, seated (or somewhat mobile) - Limited spatial resolution